Explore the vast range of titles available.

Abstract Rationale We identified a 6-year-old girl with pulmonary alveolar proteinosis (PAP), impaired granulocyte-macrophage colony–stimulating factor (GM-CSF) receptor function, and increased GM-CSF. Objectives Increased serum GM-CSF may be useful to identify individuals with PAP caused by GM-CSF receptor dysfunction. Methods We screened 187 patients referred to us for measurement of GM-CSF autoantibodies to diagnose autoimmune PAP. Five were children with PAP and increased serum GM-CSF but without GM-CSF autoantibodies or any disease causing secondary PAP; all were studied with family members, subsequently identified patients, and controls. Measurement and Main Results Eight children (seven female, one male) were identified with PAP caused by recessive CSF2RA mutations. Six presented with progressive dyspnea of insidious onset at 4.8 ± 1.6 years and two were asymptomatic at ages 5 and 8 years. Radiologic and histopathologic manifestations were similar to those of autoimmune PAP. Molecular analysis demonstrated that GM-CSF signaling was absent in six and severely reduced in two patients. The GM-CSF receptor β chain was detected in all patients, whereas the α chain was absent in six and abnormal in two, paralleling the GM-CSF signaling defects. Genetic analysis revealed multiple distinct CSF2RA abnormalities, including missense, duplication, frameshift, and nonsense mutations; exon and gene deletion; and cryptic alternative splicing. All symptomatic patients responded well to whole-lung lavage therapy. Conclusions CSF2RA mutations cause a genetic form of PAP presenting as insidious, progressive dyspnea in children that can be diagnosed by a combination of characteristic radiologic findings and blood tests and treated successfully by whole-lung lavage.

Many risk genes for the development of Alzheimer’s disease (AD) are exclusively or highly expressed in myeloid cells. Microglia are dependent on colony-stimulating factor 1 receptor (CSF1R) signaling for their survival. We designed and synthesized a highly selective brain-penetrant CSF1R inhibitor (PLX5622) allowing for extended and specific microglial elimination, preceding and during pathology development. We find that in the 5xFAD mouse model of AD, plaques fail to form in the parenchymal space following microglial depletion, except in areas containing surviving microglia. Instead, Aβ deposits in cortical blood vessels reminiscent of cerebral amyloid angiopathy. Altered gene expression in the 5xFAD hippocampus is also reversed by the absence of microglia. Transcriptional analyses of the residual plaque-forming microglia show they exhibit a disease-associated microglia profile. Collectively, we describe the structure, formulation, and efficacy of PLX5622, which allows for sustained microglial depletion and identify roles of microglia in initiating plaque pathogenesis. Genetics implicate microglia in Alzheimer’s disease pathogenesis, but their roles remain unclear. Here, the authors find that microglial depletion in a mouse model of Alzheimer’s disease impairs plaque formation and that Aβ-induced changes in neuronal gene expression are microglia-mediated.

The proliferation, differentiation and survival of mononuclear phagocytes depend on signals from the receptor for macrophage colony-stimulating factor, CSF1R. The mammalian Csf1r locus contains a highly conserved super-enhancer, the fms -intronic regulatory element (FIRE). Here we show that genomic deletion of FIRE in mice selectively impacts CSF1R expression and tissue macrophage development in specific tissues. Deletion of FIRE ablates macrophage development from murine embryonic stem cells. Csf1r ΔFIRE/ΔFIRE mice lack macrophages in the embryo, brain microglia and resident macrophages in the skin, kidney, heart and peritoneum. The homeostasis of other macrophage populations and monocytes is unaffected, but monocytes and their progenitors in bone marrow lack surface CSF1R. Finally, Csf1r ΔFIRE/ΔFIRE mice are healthy and fertile without the growth, neurological or developmental abnormalities reported in Csf1r −/− rodents. Csf1r ΔFIRE/ΔFIRE mice thus provide a model to explore the homeostatic, physiological and immunological functions of tissue-specific macrophage populations in adult animals. The lineage-specific receptor CSF1R controls macrophage development and homeostasis. Here the authors show that deletion of a conserved Csf1r enhancer (FIRE) selectively depletes brain microglia and resident macrophages in the epidermis, kidney, heart and peritoneum of otherwise healthy mice.

Arthritogenic alphaviruses, including chikungunya (CHIKV) and Mayaro virus (MAYV), cause disease characterized by fever, rash, and incapacitating joint pain. Alphavirus arthritis is associated with infiltration of myeloid cells and increases in several cytokines systemically, including granulocyte colony-stimulating factor (G-CSF). G-CSF is secreted by endothelial cells, fibroblasts, macrophages, and monocytes and binds to colony-stimulating factor 3 receptor (CSF3R, also known as G-CSFR) on the surface of myeloid cells. G-CSFR signaling initiates the proliferation, differentiation, and maturation of myeloid cells, especially neutrophils. Importantly, G-CSF has been found at high levels in both the acute and chronic phases of chikungunya disease; however, the role of G-CSF in arthritogenic alphavirus disease remains unexplored. Here, we sought to test the effect of G-CSF on CHIKV and MAYV infection using G-CSFR-deficient mice (G-CSFR ). Compared to wild-type mice, we observed sustained weight loss in G-CSFR mice following CHIKV and MAYV infection. Furthermore, G-CSFR mice had a significantly higher percentage of inflammatory monocytes and a reduction in neutrophils throughout infection. The difference in weight loss in G-CSFR mice induced by alphavirus infection was corrected by blocking type I IFN signaling. In summary, these studies suggest that type I IFN signaling contributes to G-CSFR-mediated control of arthritogenic alphavirus disease. Therefore, G-CSF or G-CSFR may be therapeutic targets to modulate host immune responses against arthritogenic alphavirus disease.

Significance We show that tumor reprogramming of hematopoiesis in bone marrow occurs at the onset of malignant conversion and results in systemic expansion of circulating activated neutrophils that preferentially accumulate in lungs. Our data are, to our knowledge, the first to show that activation and not inhibition of myeloid differentiation is responsible for expansion and activity of T cell-suppressive myeloid cells; a tumor-derived factor targets the immature hematopoietic compartment to drive myeloid expansion; granulocyte-colony stimulating factor (G-CSF) is the only hematopoietic growth factor to increase in serum during early tumor development; prolonged G-CSF induces production of Rb1 ˡᵒʷ neutrophils and not short-term mobilization; and G-CSF acts in a cell intrinsic manner to expand multipotent progenitors to increase production of tumor-derived Ly6G ⁺ neutrophils. Expansion of myeloid cells associated with solid tumor development is a key contributor to neoplastic progression. Despite their clinical relevance, the mechanisms controlling myeloid cell production and activity in cancer remains poorly understood. Using a multistage mouse model of breast cancer, we show that production of atypical T cell-suppressive neutrophils occurs during early tumor progression, at the onset of malignant conversion, and that these cells preferentially accumulate in peripheral tissues but not in the primary tumor. Production of these cells results from activation of a myeloid differentiation program in bone marrow (BM) by a novel mechanism in which tumor-derived granulocyte-colony stimulating factor (G-CSF) directs expansion and differentiation of hematopoietic stem cells to skew hematopoiesis toward the myeloid lineage. Chronic skewing of myeloid production occurred in parallel to a decrease in erythropoiesis in BM in mice with progressive disease. Significantly, we reveal that prolonged G-CSF stimulation is both necessary and sufficient for the distinguishing characteristics of tumor-induced immunosuppressive neutrophils. These results demonstrate that prolonged G-CSF may be responsible for both the development and activity of immunosuppressive neutrophils in cancer.

Microglia are resident immune cells that play critical roles in maintaining the normal physiology of the central nervous system (CNS). Remarkably, microglia have an intrinsic capacity to repopulate themselves after acute ablation. However, the underlying mechanisms that drive such restoration remain elusive. Here, we characterized microglial repopulation both spatially and temporally following removal via treatment with the colony stimulating factor 1 receptor (CSF1R) inhibitor PLX5622. We show that microglia were replenished via self-renewal, with no contribution from nonmicroglial lineages, including Nestin+ progenitors and the circulating myeloid population. Interestingly, spatial analyses with dual-color labeling revealed that newborn microglia recolonized the parenchyma by forming distinctive clusters that maintained stable territorial boundaries over time, indicating the proximal expansive nature of adult microgliogenesis and the stability of microglia tiling. Temporal transcriptome profiling at different repopulation stages revealed that adult newborn microglia gradually regain steady-state maturity from an immature state that is reminiscent of the neonatal stage and follow a series of maturation programs, including nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) activation, interferon immune activation, and apoptosis. Importantly, we show that the restoration of microglial homeostatic density requires NF-κB signaling as well as apoptotic egress of excessive cells. In summary, our study reports key events that take place from microgliogenesis to homeostasis reestablishment.

Duchenne muscular dystrophy (DMD) is a chronic and life-threatening disease that is initially supported by muscle regeneration but eventually shows satellite cell exhaustion and muscular dysfunction. The life-long maintenance of skeletal muscle homoeostasis requires the satellite stem cell pool to be preserved. Asymmetric cell division plays a pivotal role in the maintenance of the satellite cell pool. Here we show that granulocyte colony-stimulating factor receptor (G-CSFR) is asymmetrically expressed in activated satellite cells. G-CSF positively affects the satellite cell population during multiple stages of differentiation in ex vivo cultured fibres. G-CSF could be important in developing an effective therapy for DMD based on its potential to modulate the supply of multiple stages of regenerated myocytes. This study shows that the G-CSF–G-CSFR axis is fundamentally important for long-term muscle regeneration, functional maintenance and lifespan extension in mouse models of DMD with varying severities. In response to injury, satellite cells (SCs) asymmetrically divide to self-renew and repair muscle. Here the authors show that a cytokine G-CSF is crucial for long-term expansion of activated SCs and muscle regeneration in mice, suggesting that G-CSF treatment may have beneficial effect in Duchenne muscular dystrophy.

As an indispensable inflammatory mediator during sepsis, granulocyte colony-stimulating factor (G-CSF) facilitates neutrophil production by activating G-CSFR. However, little is known about the role of intracellular downstream signalling pathways in the induction of inflammation. To explore the functions of molecules in regulating G-CSFR signalling, RNA sequencing and integrated proteomic and phosphoproteomic analyses were conducted to predict the differentially expressed molecules in modulating the inflammatory response after G-CSFR expression was either up- or downregulated, in addition to the confirmation of their biological function by diverse experimental methods. In the integrated bioinformatic analysis, 3190 differentially expressed genes (DEGs) and 1559 differentially expressed proteins (DEPs) were identified in multiple-group comparisons (p < 0.05, FC >  ± 1.5) using enrichment analyses, as well as those classic pathways such as the TNF, NFkappaB, IL-17, and TLR signalling pathways. Among them, 201 proteins, especillay intercellular cell adhesion molecule-1 (ICAM1) and PKCa, were identified as potential molecules involved in inflammation according to the protein–protein interaction (PPI) analysis, and the leukocyte transendothelial migration (TEM) pathway was attributed to the intervention of G-CSFR. Compared with the control and TNF-a treatment, the G-CSFR (G-CSFROE)-overexpressing led to an obvious increase in the number of leukocytes with the TEM phenotype. Mechanically, the expression of ICAM1 and PKCa was significantly up- and downregulated by G-CSFROE, which directly led to increased TEM; moreover, PKCa expression was negatively regulated by ICAM1 expression, leading to aberrant leukocyte TEM. Altogether, the ICAM1‒PKCa axis was found a meaningful target in the leukocyte TEM induced by G-CSFR upregulation.

Sciatic nerve crush injury triggers sterile inflammation within the distal nerve and axotomized dorsal root ganglia (DRGs). Granulocytes and pro-inflammatory Ly6C high monocytes infiltrate the nerve first and rapidly give way to Ly6C negative inflammation-resolving macrophages. In axotomized DRGs, few hematogenous leukocytes are detected and resident macrophages acquire a ramified morphology. Single-cell RNA-sequencing of injured sciatic nerve identifies five macrophage subpopulations, repair Schwann cells, and mesenchymal precursor cells. Macrophages at the nerve crush site are molecularly distinct from macrophages associated with Wallerian degeneration. In the injured nerve, macrophages ‘eat’ apoptotic leukocytes, a process called efferocytosis, and thereby promote an anti-inflammatory milieu. Myeloid cells in the injured nerve, but not axotomized DRGs, strongly express receptors for the cytokine GM-CSF. In GM-CSF-deficient ( Csf2 -/- ) mice, inflammation resolution is delayed and conditioning-lesion-induced regeneration of DRG neuron central axons is abolished. Thus, carefully orchestrated inflammation resolution in the nerve is required for conditioning-lesion-induced neurorepair.

Excessive neutrophilic inflammation can contribute to the pathogenesis of pneumonia. Whilst anti-inflammatory therapies such as corticosteroids are used to treat excessive inflammation, they do not selectively target neutrophils and may compromise antimicrobial or antiviral defences. In this study, neutrophil trafficking was targeted with a granulocyte-colony stimulating factor receptor monoclonal antibody (G-CSFR mAb) during Streptococcus pneumoniae (serotype 19F) or influenza A virus (IAV, strain HKx31) lung infection in mice. Firstly, we demonstrated that neutrophils are indispensable for the clearance of S. pneumoniae from the airways using an anti-Ly6G monoclonal antibody (1A8 mAb), as the complete inhibition of neutrophil recruitment markedly compromised bacterial clearance. Secondly, we demonstrated that G-CSF transcript lung levels were significantly increased during pneumococcal infection. Prophylactic or therapeutic administration of G-CSFR mAb significantly reduced blood and airway neutrophil numbers by 30–60% without affecting bacterial clearance. Total protein levels in the bronchoalveolar lavage (BAL) fluid (marker for oedema) was also significantly reduced. G-CSF transcript levels were also increased during IAV lung infection. G-CSFR mAb treatment significantly reduced neutrophil trafficking into BAL compartment by 60% and reduced blood neutrophil numbers to control levels in IAV-infected mice. Peak lung viral levels at day 3 were not altered by G-CSFR therapy, however there was a significant reduction in the detection of IAV in the lungs at the day 7 post-infection phase. In summary, G-CSFR signalling contributes to neutrophil trafficking in response to two common respiratory pathogens. Blocking G-CSFR reduced neutrophil trafficking and oedema without compromising clearance of two pathogens that can cause pneumonia.